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Significant systemic envenoming has been defined as any of the
following:
■ neurotoxic paralysis
■ coagulopathy (confirmed by laboratory)
■ myotoxicity
■ renal impairment/failure.
Determination of the snake involved and more importantly the
selection of the appropriate monovalent antivenom is based on:
■ knowledge of the local snake fauna
■ clinical syndrome
■ snake venom detection kit.
Snake venom detection kit
The snake venom detection kit is a useful diagnostic test to
confirm which of the five major snake groups is responsible
for the envenoming. This will determine which antivenom is
needed. The test is therefore only useful in healthcare facilities
that have antivenom supplies. It should be done in a laboratory.
The test has no value in non-envenomed patients because of
false positives and it cannot be used to confirm or exclude
snake envenoming. In many cases the determination of the
snake involved can be made on geographical and clinical
grounds, and results from the venom detection kit should
always be interpreted in the context of these. It is prudent to
collect and store bite site swabs for venom detection in all
suspected snake bite cases and only do the test in cases where
envenoming is confirmed and antivenom is required.
Management of snake bite
Many snake bites do not result in envenoming. The rate of
envenoming varies depending on the species of snake. Whether
envenoming has occurred cannot be immediately determined
when the patient presents. This means all suspected snake bites
must be triaged as a medical emergency and observed for a
sufficient period of time in a hospital with adequate supplies of
antivenom and laboratory facilities. Immediate expert advice
can be obtained from the Poisons Information Centre network
(phone 13 11 26).
First aid
The bite site should not be washed so that the area can be
swabbed for venom detection. Pressure immobilisation is the
recommended first aid treatment for all snake bites. 6 It has been
effective in animal studies and case studies, but has not been
tested in clinical trials.
A broad (15 cm) bandage is applied at the same pressure as
for a sprained ankle over the entire limb. The patient must
then remain completely immobilised, not just the bitten limb.
For bites on areas other than limbs the patient should be
immobilised to slow the spread of venom.
128 | VOLUME 29 | NUMBER 5 | OCTOBER 2006
Pressure immobilisation should only be removed once the
patient is in a hospital stocked with antivenom. If the patient
is envenomed, pressure immobilisation can be removed once
antivenom therapy has commenced. If the patient has no
clinical or laboratory signs of envenoming, the bandage can
be removed if antivenom and resuscitation equipment are
available.
General management
Initial management includes basic resuscitation and assessment
of the patient. Once airway, breathing and circulation have been
assessed and stabilised, the diagnosis can be made and specific
management undertaken.
All cases of suspected snake bite should be observed for
sufficient time to exclude delayed envenoming. Close
observation is needed to look for early signs of neurotoxicity
such as ptosis. 3 There has been significant controversy over
the appropriate duration of observation and this is highly
dependent on regional snake fauna and healthcare facilities. The
current recommendation is that patients should be observed
for a period of at least 12 hours and if this period extends into
the night the patient should remain overnight. The duration
of observation may be longer in regions where delayed
envenoming occurs, for example the delayed neurotoxicity
following death adder bites in northern Australia. 4
The patient is unlikely to be envenomed if they have normal
laboratory tests on admission, 1–2 hours after pressure
immobilisation removal and before discharge.
Wound site infection is rare and only requires treatment if there
is clear clinical evidence of an infection. Local swelling often
resolves without treatment so antibiotics are not recommended.
Tetanus prophylaxis is recommended for all bites.
Antivenom
Antivenom is the mainstay of treatment in patients with
systemic envenoming (see Table 2). It is not recommended in
patients who only manifest non-specific features as these may
be misleading. Antivenom should always be administered
intravenously after 1:10 dilution with normal saline or
Hartmann's solution. The degree of dilution may need to be
modified for large volume antivenoms and in young children.
Premedication with adrenaline, antihistamines or corticosteroids
is not recommended, but the patient must be monitored in a
critical care area with adrenaline and resuscitation equipment
readily available.
After the first dose, further doses and the intervals between
them are dependent on the type of snake, the reversibility of the
clinical effects and the time it takes the body to recover once the
venom has been neutralised. The response to antivenom differs
for the various clinical and laboratory effects. The postsynaptic
neurotoxicity seen with death adder bites is reversed by